SMOOTH-MUSCLE CELL-MIGRATION INTO INTIMA AND ADVENTITIA DURING DEVELOPMENT OF TRANSPLANT VASCULOPATHY

Smooth muscle cell (SMC) migration from the medial layer into the inti ma is a characteristic feature of transplant vasculopathy and is thoug ht to be regulated by locally produced cytokines. We studied the expre ssion of smooth muscle alpha-actin, PDGF B-ligand and, PDGF alpha- and beta-receptors in rat aortic allografts with transplant vasculopathy using immunohistochemistry. At two weeks, an intense expression of PDG F B-ligand and, PDGF alpha- and beta-receptors was found in the neoint ima and adventitia. Medial SMC expression decreased with time in paral lel with accumulation of smooth muscle alpha-actin in the neointima an d adventitia. PDGF expression persisted in the adventitia. Prolonged i schemic storage time resulted in an increase in the number of alpha-ac tin-positive SMCs in the intima of syngeneic grafts. These data indica te that SMCs migrate into both the intima and adventitia. This migrati on may be induced, at least in part, by PDGF produced by graft invadin g monocyte-derived macrophages.